In the description which follows, reference is made primarily to the eye. This has to be understood as merely a way to help the description and not as a restriction of the application of the present invention. As such, where the term “eye” is used, a more general transparent and scattering object or organ may be sought instead, the invention could equally be applied to skin, heart, vessels, embryos, dental tissue, dental prostheses, paintings, powders and other scattering semi-transparent objects.